JPH0974116A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a reflow while maintaining the higher temperature than the melting point of a solder bump in the state that the solder bump is immersed in a liquid in order to enhance the reliability of a bonding part by surely performing the flip chip bonding of a bare chip and a wiring board. SOLUTION: After a solder bump is formed in the electrode pad part of a bare chip (Step S1), the electrode pad of the bare chip is accurately positioned on a wiring board (Steps S2, S3). Next, the chip is temporarily fixed by applying a load thereto (Step S4). The whole of the wiring board on which the temporarily fixed bare chip is mounted is immersed into a liquid inside a container (Step S5), and the reflow of solder is performed by increasing the temperature of the whole of the liquid up to the higher temperature than the melting point of the solder bump while maintaining that condition (Step S6). When the reflow is finished, the temperature of the liquid is decreased to take out the bare chip and the wiring board and to clean up the liquid (Step S7).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flip-chip connection type semiconductor device in which an integrated circuit device is directly connected to a wiring board and a method for manufacturing the semiconductor device.

[0002]

2. Description of the Related Art Conventionally, in order to cope with an increase in the number of I / Os in an integrated circuit device and a tendency toward miniaturization of the integrated circuit device, as a mounting method, an electrode pad is directly attached to a wiring board while the integrated circuit chip is a bare chip. Flip-chip connections are used that electrically connect to the corresponding pads.

FIG. 10 shows a flip-chip connected substrate and a chip. In the flip chip connection method, solder bumps (bumps) 2 are formed on the electrode pads of the bare chip 1. Then, with the paired chip 1 face down, the electrode pads are accurately aligned on the wiring board 3 and a load is applied to temporarily fix the chip 1 to the wiring board 3. After that, the solder is reflowed by exposing it to an atmosphere having a temperature higher than the melting point of the solder bump 2 (for example, 200 ° C. or higher). As a result, the chip 1 and the electrode pads of the wiring board 3 are directly connected to each other.

According to this method, the number of electrode pads can be increased and the pitch can be made finer, and the connection distance between the integrated circuit chip and the wiring board can be shortened, so that the integrated circuit operates at high speed in the mounted state. Will be possible.

[0005]

However, according to the above-mentioned flip-chip connection method, it is difficult to reliably connect all the electrode pads, and the connection of some pads often becomes defective. I have a problem. One of the causes for this is that the temporarily fixed chip is easily displaced if an external force is applied to the chip during the transportation from the time when the chip is temporarily fixed to the wiring board until the connection by reflow.

For example, as shown in FIG. 11, when the chip 1 is temporarily fixed to the wiring board 3 and vibration is applied in the direction indicated by the arrow A, the weight of the chip 1 is not enough to obtain the solder bumps 2. I cannot hold it. As a result, the chip 1 comes off from the wiring board 3.

Also in the double-sided wiring board 3 as shown in FIG. 12, it is possible that the weight of the chip cannot be supported similarly. That is, the gravity indicated by arrows B and B'in the figure is applied to the chips 1 and 1'temporarily fixed on the wiring board 3. Therefore, the solder bumps 2'cannot support the chip 1'and come off.

Further, as another cause of the pad connection failure, if an external force is applied to the chip while reflowing the substrate on which the chip is temporarily fixed, the reflowed bump cannot support the chip and the chip comes off. It can be mentioned.

FIG. 13 shows an example of a case where the problem of poor connection of the pad occurs. For example, solder bump 2
Is crushed by the gravity B applied to the chip 1 on the wiring board 3, and as a result, there is a risk of contact with other adjacent electrode pads. In the case of a double-sided mounting board, the solder bumps 2 ′ are extended by the gravity B ′ applied to the chip 1 and the chip 1
May come off from the wiring board 3.

Alternatively, as shown in FIG. 14, the flux 4 applied to the solder bumps 2 is vaporized during the reflow process, and the pressure may cause the chip 1 to be detached from the wiring substrate 3.

Another cause of defective connection of some electrode pads is that all solder bumps cannot be reliably heated to a temperature higher than the melting point during reflow, and some or all of the pads cannot be connected. It can be mentioned that the solder bump corresponding to the above does not melt. This causes the occurrence of such a defect because a temperature distribution is generated between the heater unit of the reflow furnace or the like and the chip / substrate bonded body.

As another problem in flip-chip connection, it is necessary to use flux during reflow in order to prevent the solder bumps from being oxidized while the solder is hot during reflow. It can be mentioned. This deteriorates the reliability of the solder connection portion due to the flux residue after the flux cleaning.

The present invention has been made in view of the above problems, and an object of the present invention is to perform connection in a flip chip connection between a bare chip and a wiring board by surely connecting the chip and the wiring board. It is an object of the present invention to provide a semiconductor device capable of preventing failure and a method of manufacturing the semiconductor device.

[0014]

That is, according to the present invention, the first step of forming a solder bump on an electrode pad provided on a semiconductor chip and the solder bump facing the electrode provided on a wiring board are performed. A second step of temporarily fixing the semiconductor chip on the wiring board, a third step of immersing at least the solder bump in a liquid, an electrode pad of the semiconductor chip and the wiring board via the solder bump. In order to electrically connect with the upper electrode, a fourth step of performing reflow of the solder bump while holding the liquid at a temperature higher than the melting point of the solder bump is provided.

According to the present invention, the first step of forming a solder bump on an electrode pad provided on a semiconductor chip and the above-mentioned wiring bump on the wiring board by facing the solder bump to an electrode provided on the wiring board. A second step of temporarily fixing the semiconductor chip, a third step of covering the semiconductor chip with a closing member and fixing the closing member on the wiring board, and a fourth step of injecting a liquid into the closing member. Step, a fifth step of reflowing the solder bump while holding the liquid at a temperature higher than the melting point of the solder bump, and a sixth step of removing the blocking member from the wiring board. It is characterized by

Further, according to the present invention, a first step of forming a solder bump on an electrode pad provided on a semiconductor chip, a second step of immersing the solder bump in a liquid, and a step of dipping the liquid in the solder bump. And a third step of reflowing the solder bump while maintaining the temperature higher than the melting point.

Further, in the semiconductor device of the present invention, at least one semiconductor chip, the solder bumps formed on the electrode pads of the semiconductor chip, and the electrodes arranged to face the solder bumps, A wiring board to which the semiconductor chip is electrically connected via the solder bumps, a closing member having the semiconductor chip therein and fixed on the wiring board, and a wiring board housed in the closing member The semiconductor chip is dipped, and a liquid that is kept at a temperature higher than the melting point of the solder bump during reflow is provided.

According to the present invention, the solder bumps of the semiconductor chip to be flip-chip connected are reflowed while being immersed in the liquid at a temperature higher than the melting point of the solder bumps. As a result, the external force due to vibration during transportation and reflow after being temporarily fixed and then immersed in a liquid is reduced. By immersing the chip and the wiring board in a liquid, the buoyancy acting on the chip is used to control the force applied to the bump.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a flow chart for explaining the operation of the first embodiment of the present invention, and FIG. 2 is a diagram showing a manufacturing process of a semiconductor device according to the first embodiment.

First, as shown in FIG. 2A, solder bumps 12 are formed on the electrode pads of the bare chip 11.
Are formed (step S1). And bare chip 1
1 is face down, and the bare chip 11 is placed on the wiring substrate 13.
The electrode pads of are accurately aligned (step S
2, S3). Then, by applying a load, as shown in FIG.
As shown in, the chip 11 is temporarily fixed to the wiring board 13 (step S4).

Next, the entire wiring board 13 on which the temporarily fixed bare chip 11 is mounted is immersed in a container 15 containing a liquid 14 as shown in FIG. 2 (c). That is, the wiring board 13 on which the bare chip 11 is mounted is immersed in the liquid 14 (step S5). Then, with the bare chip 11 and the wiring substrate 13 being immersed, the liquid 1 is heated to a temperature higher than the melting point of the solder bump 12.
The entire 4 is heated to reflow the solder (step S6).

After that, until the solder bumps 12 are completely melted and the electrodes of the wiring substrate 13 and the bare chip 11 are fully wetted, the temperature higher than the melting point of the solder bumps 12 is maintained. .

As the kind of the liquid 14, a liquid which is stable up to a high temperature and is not corrosive is desirable. For example, silicone oil having a specific gravity close to that of water and a specific heat larger than that of air is suitable.

When the reflow is completed, the temperature of the liquid 14 is lowered to room temperature, and the bare chip 11 and the wiring substrate 13 are
Is taken out and the liquid 14 is washed (step S7).
Thus, the flip chip connection is completed.

As described above, in the first embodiment, since the reflow is performed in the liquid, the liquid serves as a cushion, and external vibration during the reflow directly affects the bonded body of the chip and the substrate. It prevents you from joining. Therefore, it is possible to prevent a connection failure due to an external force due to vibration during transportation and reflow after the chip is temporarily fixed to the substrate and then immersed in the liquid.

Further, since the reflow is performed in a liquid having a specific heat larger than that of the air as compared with the conventional example, the temperature controllability is good and the solder bumps on all the electrode pads are heated to a uniform temperature during the reflow. It is also possible to let it.

As described above, the solder bumps can be prevented from coming into contact with the outside air when the solder is at a high temperature during reflow. This means that it is not necessary to remove the surface oxide film of the solder by using flux at the time of reflow because the oxidation of the solder can be prevented especially in a high temperature state. It is not preferable to use the flux during the reflow, because the flux residue after cleaning deteriorates the reliability of the solder joint. However, in the first embodiment, the stable connection can be made without using the flux, so that the deterioration of the reliability of the solder connection portion can be prevented.

Next, a second embodiment of the present invention will be described. FIG. 3 illustrates a second embodiment of the present invention, and illustrates a reflow state in flip-chip connection between a wiring board and a bare chip.

Similar to the first embodiment shown in FIG. 2, in FIG. 3, the entire wiring substrate 13 in which the bare chip 11 is temporarily fixed is immersed in the liquid 14 and the solder bumps 12 are formed. The temperature of the entire liquid 14 is raised to a temperature higher than the melting point of, and the solder is reflowed. At this time, the wiring board 13
Is held by a carrier which is fixed by sandwiching its edge, and is fixed to the container 15. That is, the wiring board 13
On the other hand, the bare chip 11 is fixed so as to face upward in the drawing.

In this state, the weight of the bare chip 11 causes the gravity of the bare chip 11 in the direction of the arrow D in FIG.
Therefore, the buoyancy in the direction of arrow E in the figure is applied in the opposite direction. The sum of gravity and buoyancy of the chip 11 is the solder bump 12
It is the vertical force applied to the whole.

The buoyancy applied to the tip 11 is determined by the specific gravity of the liquid 14 soaked. Therefore, liquid 1
By changing the specific gravity of No. 4, the force applied to the solder bump 12 can be controlled. This is shown in FIGS.
As shown in (1), it means that the occurrence of connection failure due to gravity or other external force applied to the chip 11 can be prevented by changing the magnitude of the external force by buoyancy.

Further, in the second embodiment, in addition to preventing the connection failure, the shape of the solder bump 12 after connection is controlled by controlling the force applied to the reflowed solder bump 12. You can also Since the stress applied to the bump after connection differs depending on the bump shape, the reliability of the solder connection portion can be improved by controlling the bump shape so that the stress becomes small.

FIG. 4 shows a modification of the above-described second embodiment of the present invention. Similarly to FIG. 3, the entire wiring substrate 13 is immersed in the liquid 14 to remove the solder bump 1
The entire liquid 14 is heated to a temperature higher than the melting point of 2'and the solder is reflowed. At this time, with the wiring board 11 fixed to the container 15 by the carrier 16, the chip 11 'is directed downward (in the direction of the arrow D'in the drawing) with respect to the board 11. In this case, the force applied to the solder bump 12 'can be set in the direction opposite to that in the case of FIG. 3, and the controllable range of the bump shape after connection can be widened.

Next, a third embodiment of the present invention will be described. FIG. 5 is a diagram for explaining the third embodiment of the present invention, showing a reflow state in flip-chip connection between a wiring board and a chip.

Solder bumps 1 are formed on both upper and lower surfaces of the wiring board 11.
Bare chips 11 and 11 'are temporarily fixed by 2 and 12'. Then, the entire substrate 13 to which the chips 11 and 11 'are temporarily fixed is placed in a carrier 16 in a liquid heated to a temperature higher than the melting points of the solder bumps 12 and 12'.
The solder is reflowed by being dipped while being supported by. The specific gravity of the liquid 14 in this case is the chip (Si)
It is adjusted to almost the same as.

In this state, gravity (D and D ') due to the weight of the die chip and buoyancy (E and E') due to the liquid 14 are applied to the chips 11 and 11 'above and below the substrate 13 in opposite directions. Therefore, the sum of the gravity and the buoyancy of the chips 11 and 11 'becomes the vertical force applied to the entire solder bumps 12 and 12'. In this case, the gravity (D and D ') and the buoyancy (E and E') applied to the chips 11 and 11 'are substantially equal in magnitude and opposite in direction, and no force is applied to the solder bumps 12 and 12'.

Therefore, the solder bumps 12 and 12 'for connecting the upper and lower chips 11 and 11' of the substrate 13 are connected under the same condition without any load applied during reflow. Therefore, it is possible to prevent the upper and lower connection bump shapes from becoming different shapes due to the difference in load applied to the bumps.

Next, a fourth embodiment of the present invention will be described. FIG. 6 shows a fourth embodiment of the present invention and is a side sectional view of a semiconductor device.

In FIG. 6, solder bumps 12 are formed on the electrode pads of the bare chip 11. And
The bare chip 11 is faced down, the electrode pads are accurately aligned on the wiring board 13, and the bare chip 11 is temporarily fixed to the wiring board 13 by applying a load.

A cap 17 is fixed on the wiring board 13 by a sealing method or the like. The cap 17 is fixed on the substrate in order to keep the bare chip 11 immersed in the liquid 14, and is composed of a member that can withstand the reflow temperature. Further, the cap 17 is provided with a hole 18a for injecting the liquid, and after the injection of the liquid 14, the hole 18a is closed by the lid member 18b which can be opened and closed so that the liquid 14 is sealed in the cap 17. It has become. That is, the chip 11 temporarily fixed on the wiring board 13 is immersed in the liquid 14.

As the kind of liquid, it is desirable that the liquid is stable up to a high temperature and is not corrosive as in the first embodiment. Then, the temperature of the entire liquid 14 is raised to a temperature higher than the melting point of the solder bump 12, and the solder is reflowed. This reflow is maintained at a temperature higher than the melting point of the solder bump 12 until the solder bump 12 is completely melted and sufficient wettability is ensured for the wiring board 13 and the electrodes of the bare chip 11. Then, when the temperature of the liquid 14 drops to room temperature, the cap 17 is removed, the liquid is washed, and the flip chip connection is completed.

As described above, in the fourth embodiment, since the reflow is performed in the liquid, there is an effect that the chip is protected as in the first embodiment described above. Further, since the reflow is performed while the substrate is fixed, the same effect as the second embodiment can be obtained.

In the example of FIG. 6, one bare chip 11 is mounted on one wiring board 13, but as shown in FIG. 7, a plurality of bare chips 11 are mounted on the same board 13.
You may mount a, 11b. In this case, bare chip 1
One cap for each.

Further, as shown in FIG. 8, the wiring board 1
When the bare chips 11 and 11 'are mounted on both surfaces of the cap 3, caps 17 and 17' are provided for the bare chips 11 and 11 ', respectively.

Then, as shown in FIGS. 7 and 8,
When mounting a plurality of bare chips 11a, 11b or 11, 11 'on the same substrate 13, a liquid 14a to be dipped,
14b or 14, 14 'with caps 17a, 17b
Alternatively, each of 17 and 17 'can be different. As a result, the force applied to the bump during reflow can be controlled separately for each bare chip.

Although the cap 17 is removed after the solder reflow in the fourth embodiment, the cap 17 may be left as it is. In this case, the heat of the cap is transferred to the cap by the silicone oil to improve the heat dissipation effect, and the oxidation of the solder bumps is prevented, so that the reliability is improved.

FIG. 9 shows a fifth embodiment of the present invention and is a view showing a state of the semiconductor device at the time of reflow. In FIG. 9, solder bumps 12 are formed on the electrode pads of the bare chip 11. The bare chip 11 is not mounted on the wiring board, but is immersed in the liquid 14 in the container 15.

That is, the fifth embodiment is applied when reflowing the bumps on the chip. According to the fifth embodiment, the temperature during reflow can be easily controlled.

[0049]

As described above, according to the present invention, in the flip chip connection between the bare chip and the wiring board, the chip and the wiring board can be surely connected to each other to prevent the connection failure. A device and a method for manufacturing the semiconductor device can be provided.

[Brief description of drawings]

FIG. 1 is a flowchart explaining an operation of a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the semiconductor device according to the first embodiment.

FIG. 3 illustrates a second embodiment of the present invention.
It is a figure showing a reflow state in flip-chip connection of a wiring board and a bare chip.

FIG. 4 is a view showing a modified example of the second embodiment of the present invention and is a diagram showing a reflow state in flip-chip connection between a wiring board and a bare chip.

FIG. 5 illustrates a third embodiment of the present invention.
FIG. 6 is a diagram showing a reflow state in flip-chip connection between a wiring board and a chip.

FIG. 6 shows a fourth embodiment of the present invention and is a side sectional view of a semiconductor device.

FIG. 7 shows a modified example of the fourth embodiment of the present invention and is a side sectional view of a semiconductor device.

FIG. 8 is a side sectional view of a semiconductor device, showing another modification of the fourth embodiment of the present invention.

FIG. 9 illustrates a fifth embodiment of the present invention and is a diagram showing a state of the semiconductor device during reflow.

FIG. 10 is a view showing a conventional flip-chip connected substrate and chip.

FIG. 11 is a diagram showing an example of problems in the conventional flip chip connection.

FIG. 12 is a diagram showing another example of problems in the conventional flip-chip connection.

FIG. 13 is a diagram showing an example of a case where a pad connection problem occurs in the conventional flip chip connection.

FIG. 14 is a diagram showing an example of connection failure due to vaporization of flux in conventional flip-chip connection.

[Explanation of symbols]

1, 1 ', 11, 11', 11a, 11b ... Bare chips (chips), 2 ', 12, 12' ... Solder bumps,
3, 13 ... Wiring board, 14, 14 ', 14a, 14b ...
Liquid, 15 ... Container, 16 ... Carrier, 17, 17 ', 1
7a, 17b ... Cap, 18a ... Hole, 18b ... Lid member.

Claims (24)

[Claims] 1. A first step of forming a solder bump on an electrode pad provided on a semiconductor chip; and a step of placing the semiconductor chip on the wiring board by facing the solder bump to an electrode provided on the wiring board. Second step of temporarily fixing, third step of immersing at least the solder bump in a liquid, and electrically connecting the electrode pad of the semiconductor chip and the electrode on the wiring board via the solder bump In order to
And a fourth step of reflowing the solder bumps while holding the liquid at a temperature higher than the melting point of the solder bumps. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a plurality of the semiconductor chips are provided on the same surface of the wiring board. 3. The semiconductor chip according to claim 1, wherein at least one semiconductor chip is provided on a first surface of the wiring board and on a second surface opposite to the first surface. Of manufacturing a semiconductor device of. 4. The third step is characterized in that the semiconductor chip and the wiring board connected to the semiconductor chip via the solder bumps are dipped in a liquid. 4. The method for manufacturing a semiconductor device according to any one of 3 above. 5. The method of manufacturing a semiconductor device according to claim 4, wherein the third step further includes a step of fixing at least the wiring board in the liquid. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the liquid has a specific gravity close to that of water and a specific heat larger than that of air. 7. The method of manufacturing a semiconductor device according to claim 6, wherein the liquid is composed of silicon oil. 8. A first step of forming a solder bump on an electrode pad provided on a semiconductor chip, and the semiconductor chip on the wiring board with the solder bump facing an electrode provided on the wiring board. A second step of temporarily fixing, a third step of covering the semiconductor chip with a closing member and fixing the closing member on the wiring board, and a fourth step of injecting a liquid into the closing member. A fifth step of reflowing the solder bumps while holding the liquid at a temperature higher than the melting point of the solder bumps, and a sixth step of removing the blocking member from the wiring board. And a method for manufacturing a semiconductor device. 9. The method of manufacturing a semiconductor device according to claim 8, wherein a plurality of the semiconductor chips are provided on the same surface of the wiring board, and each semiconductor chip is covered with each closing member. 10. At least one semiconductor chip is provided on the first surface of the wiring board and on a second surface opposite to the first surface, and the semiconductor chip is covered with each closing member. 9. The method of manufacturing a semiconductor device according to claim 8, wherein 11. The method of manufacturing a semiconductor device according to claim 8, wherein the closing member has heat resistance up to a temperature higher than a melting point of the solder bump. 12. The method of manufacturing a semiconductor device according to claim 8, wherein the closing member has an injection hole for injecting the liquid. 13. The method of manufacturing a semiconductor device according to claim 8, wherein the liquid has a specific gravity close to that of water and a specific heat larger than that of air. 14. The method of manufacturing a semiconductor device according to claim 13, wherein the liquid is composed of silicon oil. 15. A first step of forming a solder bump on an electrode pad provided on a semiconductor chip, a second step of immersing the solder bump in a liquid, and the liquid being higher than the melting point of the solder bump. And a third step of reflowing the solder bump while maintaining the temperature. 16. The method of manufacturing a semiconductor device according to claim 15, wherein the liquid has a specific gravity close to that of water and a specific heat larger than that of air. 17. The method of manufacturing a semiconductor device according to claim 16, wherein the liquid is composed of silicon oil. 18. At least one semiconductor chip, a solder bump formed on an electrode pad of the semiconductor chip, and an electrode provided so as to face the solder bump, the semiconductor chip being mounted on the electrode via the solder bump. A wiring board that is electrically connected, a closing member that has the semiconductor chip inside and is fixed on the wiring board, and the semiconductor chip is immersed in the closing member to immerse the semiconductor chip, and the solder is used during reflow. A liquid crystal held at a temperature higher than the melting point of the bump, the semiconductor device. 19. The semiconductor device according to claim 18, wherein the liquid has a specific gravity close to that of water and a specific heat larger than that of air. 20. The semiconductor device according to claim 19, wherein the liquid is composed of silicon oil. 21. The semiconductor device according to claim 18, wherein the closing member has heat resistance up to a temperature higher than a melting point of the solder bump. 22. The semiconductor device according to claim 18, wherein the closing member has an injection hole for injecting the liquid. 23. A plurality of the semiconductor chips are provided on the same surface of the wiring board.
The semiconductor device according to. 24. At least one semiconductor chip is provided on each of a first surface of the wiring board and a second surface opposite to the first surface. The semiconductor device described.